Immune function is a basic function possessed by animals for keeping life, by selectively excluding such a case that a pathogen or the like which is disadvantageous to the existing of themselves invades into the body or a cancer or the like is generated therein. The immunological function is realized by mutual cooperation and regulation of various lymphocytes, macrophages, leukocytes and the like distributed mainly in thymus and also in spleen, lymph node, bone marrow and the like.
A drug which improves the immunological function is useful as a preventive or therapeutic agent for cancers, a therapeutic agent for various autoimmune diseases and the like, as well as a medicine or food for increasing resistance to various infections and the like. It is the that, among a large number of amino acids, glutamine and arginine have the action to improve immunological function (Patent Reference 1).
In addition, it is broadly known that active oxygens typified by superoxide radical and hydrogen peroxide have cytotoxicity and are the cause of cancer, rheumatism, spots, wrinkles and the like. Also, it is known that LDL which carries cholesterol is changed to oxidized LDL by active oxygen, and the changed oxidized LDL becomes a cause of arteriosclerosis.
Thus, since it is said that a pharmaceutical agent having an antioxidation action is useful in preventing or treating life-style diseases such as arteriosclerosis, cancer and diabetes mellitus, abnormal pigmentation such as spots and freckles, inflammation of the skin, senescence of the skin and the like, various antioxidation action components have been found. For example, it is known that the antioxidation action can be found in natural substances such as vitamin E and vitamin C, synthetics such as BHT (3,5-tert-butyl-4-hydroxytoluene) and BHA (2,3-tert-butyl-hydroxyanisole), crude drugs and the like (Patent Reference 2).
On the other hand, health function of human and animals is reduced by fatigue, disease, pregnancy, aging, nutritional disorder or poor nutrition. This fatigue includes physical fatigue and mental fatigue, and not only physical fatigue but also mental fatigue is greatly concerned in the fatigue of the moderns.
Among these, a complex carbohydrate of saccharides and starch and the like are used as a nourishment effective for the physical fatigue. Also, as medicaments, a vitamin B group such as vitamin B1, vitamin B2 and nicotinic acid, melatonin, vitamin C, vitamin E, magnesium and the like are used.
In addition, it has been reported recently that amino acids of a specific composition containing essential amino acids and nonessential amino acids have an effect to improve exercise function at the time of fatigue (Patent Reference 3). The essential amino acids include valine, leucine, isoleucine, lysine, threonine, methionine and the like, and the nonessential amino acids include arginine, glutamine, proline and the like.    Patent Reference 1: JP-A-2002-3372    Patent Reference 2: JP-A-10-139678    Patent Reference 3: JP-A-9-249556